System and method for diagnosing a condition of an engine from volcanic ash found in lubricating fluid

A method and system for diagnosing a condition of an air-breathing aircraft engine are described. The method comprises obtaining a sample of lubricating fluid from the engine, filtering the sample to obtain a plurality of particles from the lubricating fluid, obtaining chemical composition data for the plurality of particles, determining a quantity of volcanic ash in the lubricating fluid by considering each one of the particles as composed partially of volcanic ash and partially of at least one other material and analyzing the chemical composition data, the volcanic ash having associated thereto a predetermined chemical composition, and diagnosing a condition of the engine based on the quantity of volcanic ash found in the lubricating fluid.